Near field RF (radio frequency) communication requires an antenna of one near field RF communicator to be present within the alternating magnetic field (H field) generated by the antenna of another near field RF communicator by transmission of an RF signal (for example a 13.56 Mega Hertz signal) to enable the magnetic field (H field) of the RF signal to be inductively coupled between the communicators. The RF signal may be modulated to enable communication of control and/or other data. Ranges of up to several centimetres (generally a maximum of 1 metre) are common for near field RF communicators.
Near field communication may be referred to as near-field RFID (Radio Frequency Identification) or near-field communication. NFC communicators are a type of near field RF communicator that is capable of both initiating a near field RF communication (through transmission or generation of an alternating magnetic field) with another near field RF communicator and of responding to initiation of a near field RF communication by another near field RF communicator. The term “near field RF communicator” includes not only NFC communicators but also initiating near field RF communicators such as RFID transceivers or readers that are capable of initiating a near field RF communication but not responding to initiation of a near field RF communication by another near field RF communicator and responding near field RF communicators such as RFID transponders or tags that are capable of responding to initiation of a near field RF communication by another near field RF communicator but not of initiating a near field RF communication with another near field RF communicator. Hence NFC communicators can act as both RFID transceivers and RFID transponders and are able to communicate with other NFC communicators, RFID transceivers and RFID transponders.
Examples of near field RF communicators are defined in various standards for example ISO/IEC 18092, ISO/IEC 14443, ISO/IEC 15693 ISO/IEC 21481.
NFC communicators may be provided as standalone or discrete devices or may be incorporated within or coupled to larger electrical devices or host devices (referred to below as NFC communications enabled devices) to enable those devices to communicate by the near field with other near field RF communicators or devices incorporating or coupled to such near field RF communicators. When incorporated within a larger device or host, a NFC communicator may be a discrete entity or may be provided by functionality within the larger device or host. Examples of such larger devices or host devices are, for example, mobile telephones, portable computing devices (such as personal digital assistants, notebooks, lap-tops), other computing devices such as personal or desk top computers, computer peripherals such as printers, or other electrical devices such as portable audio and/or video players such as MP3 players, IPODs®, CD players, DVD players.
NFC communicators and host devices of course require a power supply to function. Where an NFC communicator or host device incorporating or coupled to an NFC communicator is powered by a chargeable power supply such as a rechargeable battery, then maintenance of a sufficient power supply is of prime importance to the functioning of both the host device and the NFC communicator, particularly where the NFC communicator or host device is being used in circumstances in which charging of the battery using a mains charging unit is not possible, for example because the user of the NFC communicator or host device does not have the mains recharging unit with them or is in a location without access to a mains power supply point. These power supply issues may be exacerbated for a host device because the NFC communicator may place an additional drain on the chargeable power supply of the host device. Additionally absence of suitable power supply may prevent or interrupt near field RF communication between one NFC communicator and another near field RF communicator. Depending on the application of such communication this could result in a failure to complete a required function or action, for example, a failure to obtain access to a location, refusal of a ticket to travel, inability to purchase goods or transfer data or information between electrical devices.